Method and apparatus for the continuous manufacture of a flexible waveguide

ABSTRACT

Method and apparatus for manufacturing long lengths of flexible waveguides which have an inner wall of a helically wound insulated conductor covered by insulating or metal tape over which a thermoplastic sheath is extruded, in which the insulated conductor is wound in a helix and advanced successively through tape winding and sheath extruding machines at a rate which permits each operation to be continuous. Subsequent to the extrusion of the sheath it is cooled and the waveguide is wound on a bobbin. Armoring and protective layers may be added to the waveguide prior to or subsequent to winding of the waveguide on the bobbin.

United States Patent [1 1 Priaroggia et al.

[ METHOD AND APPARATUS FOR THE CONTINUOUS MANUFACTURE OF A FLEXIBLEWAVEGUIDE [75] Inventors: Paolo Gazzana Priaroggia, Milan;

Antonio Portinari, Sesto San Giovanni, both of Italy [73] Assignee:Industrie Pirelli Societe Per Azioni Centro Pirelli, Milan, Italy [22]Filed; May 3, 1971 [21] Appl. No.: 139,633

[30] Foreign Application Priority Data May 8, 1970 Italy 24300 A/70 [56]References Cited UNITED STATES PATENTS 3,391,525 Ostennann 57/9 Nov. 6,1973 Primary Examiner-Charles W. Lanham Assistant ExaminerCarl E. HallAttorney-Brooks, Haidt & Haffner [57] ABSTRACT Method and apparatus formanufacturing long lengths of flexible waveguides which have an innerwall ofa helically wound insulated conductor covered by insulating ormetal tape over which a thermoplastic sheath is extruded, in which theinsulated conductor is wound in a helix and advanced successivelythrough tape winding and sheath extruding machines at a rate whichpermits each operation to be continuous. Subsequent to the extrusion ofthe sheath it is cooled and the waveguide is wound on a bobbin. Armoringand protective layers may be added to the waveguide prior to orsubsequent to winding of the waveguide on the bobbin.

4 Claims, 1 Drawing Figure METHOD AND APPARATUS FOR THE CONTTNUOUSMANUFACTURE OF A FLEXIBLE WAVEGUIDE The present invention concernsmethod and apparatus for the manufacture of a flexible type of helicalwaveguide in a continuous manner and in relatively long lengths.

Examples of the types of waveguides to which the invention applies areshown and described in our copending application (P-333), filedconcurrently herewith and entitled Improved Helical Waveguide. Suchwaveguides have an internal helix of insulation covered metal which iscovered with a layer of insulating or metal tape. A'sheath in the formof a layer'of thermoplastic material is extruded over the layer of tape,and such sheath is normally covered by an armor, such as a layer ofwires. Normally, also, the armor is covered by an external protectivelayer, such as a layer of impregnated jute or a layer of thermoplasticmaterial. Although said application shows only the use of metal strapfor the helix, this invention is equally applicable to the manufactureof helical waveguides having a helix made of a conductor having adifferent cross-section, e.g. circular.

The process in use up to the present time for the manufacture of helicalwaveguides enables the manufacture of sections of guide having only alimited length of a few meters and which, during installation, have tobe connected together using a corresponding number of joints which, eventhough the connecting operation is carried out with the utmost care,produces points of discontinuity that inevitably lead to losses intransmission of the main wave mode.

Such known process comprises winding on a mandrel a helical coil ofinsulated wire with the turns in good alignment and near to one anotherand in subsequently covering the resulting helix with a sheath ofsynthetic resin.

The present invention aims at providing a process for the continuousmanufacture of flexible helical wave guides, the length of which islimited only by the capacity of the take-up bobbin, so that in aninstallation the joints are reduced to a minimum and consequently thelosses due to discontinuities decreases.

In particular, the present invention aims at providing a process for themanufacture of a flexible type of helical waveguide, by means of whichthe helix is formed by winding a conductor on a suitable device,characterized by the fact, that it consists in the continuous formationof this helix while simultaneously moving it along in the directionofits axis at a speed synchronized with that of the formation of asynthetic resin sheath thereon by extruding the material of the sheathon the advancing helix.

A further object of the invention is to provide apparatus designed tocarry out the process according to the invention, characterized by thefact that such apparatus comprises: a wire-distributor head on a devicedesigned to receive the helix being formed and to guide it in thedirection of its axis, a pressure and pulling device designed to adjustthe speed of movement of the helix and synchronize it with the formationspeed, and following such-device at least one extrusion head forextruding a sheath on the advancing helix.

The attached drawing illustrates by way of a nonlimiting example, apresently preferred embodiment of the invention, and such drawing, I

The FIGURE represents diagrammatically a production line includingapparatus which permits the process to be carried out according to theinvention.

The production line and apparatus shown in FIG. 1 comprises awire-distributor head 10, a device 11 designed to receive the helixbeing formed and guide it onwards. The device 11 is, for example, amandrel either fixed or, if desired, rotating on its own axis whichextends for length starting with the helical waveguide formation up to apoint at which the helix is stabilized. A pressure and waveguide pullingdevice 12 is arranged around the mandrel 11, and the devicelZ preferablyis composed of four drive elements, each including a continuous elasticbelt 20 extending around two rollers 21, at least one of which is drivenso that the portion of the belt which contacts the helix 24 moves thehelix from left to right as viewed in FIG. 1. The number of these driveelements can obviously be different from four or the pulling device 12could be another conventional pulling device.

A lapping head 13 is situated downstream from the device 12 and isfollowed in order, by an extruder 14 and a cooling bath 15, containing asecond pulling device 16 for the adjustment of the axial load on thewaveguide. Such device 16 as in the case of pulling device 12, comprisesfour elements, each comprising an elastic belt 22 moved by at least oneofa pair of rollers 23. As with the pulling device 12, the number ofelements making up the pulling device 16 could be different from four orthe device 16 could be another known type of pulling device.

A rotatable bobbin 18 takes up the waveguide 17 at the end of themanufacturing process.

The forming head 10 rotates around the mandrel 1 1 and winds on thelatter helix-24 of metal strap or wire made of insulated conductivematerial (for example, enamelled metal strap or copper wire), so thatthe turns are wound in perfect close relation, one with the other. Thehead 10 may wind only a single insulated conductor on the mandrel 11 orcould wind simultaneously on to the mandrel 11 a plurality of insulatedconductors with their turns interposed and in contact in the event thatfor construction reasons the helices called for a higher winding pitchthan that obtained with only one.

conductor.

The helix resulting from the simultaneous winding on to the mandrel 1 lof a plurality of insulated conductors is called a multi-start helix.The multi-start helix could also be obtained by uniting a number ofmetal straps and subsequently winding the element obtained on themandrel.

The helix 24 on coming out from the forming head 10 is gripped betweenthe elements constituting the pressure and pulling device 12 which, bythe belts 20 moved by the rollers 21, force the helix to advance at aspeed which is synchronized with that ofthe formation of the helix. Thedevice 12, in addition to being an adjusting unit which enables theadvancing speed to be the same as the speed of the helix formation, isalso a device which permits the necessary pressure to be applied to theturns of the helix to keep them perfectly adjacent for the whole oftheir travelling time towards the next production phase of thewaveguide.

Downstream of the device 12, the helix 24 is immediately covered with awrapping 25 of tapes made of a suitable material, for example plastic ormetallic, by the lapping head 13 rotating round the axis of the helix.As shown in the drawing, the width of the tape 25 is greater than thedistance between corresponding points on adjacent turns of the helix 24.

The helix wrapped in this way enters the extrusionhead 14, where it iscovered with a sheath 26 of thermoplastic resin (for examplepolyethylene or polyvinylchloride.) At this point, the waveguide iscomplete and it is subsequently passed into the cooling bath l and intothe device 16 for the regulation of the axial drive applied to it. v

The application of armoring and protective layers to the waveguide, ifrequired and which have the object of making the sections less liable tochanges during the bending and laying operations, can be carried outdirectly on the line in a subsequent operation, either between thecooling bath and the take-up on the bobbin 18, or in a subsequentoperation after the take-up phase. I

It is evident that with the process and the apparatus of the presentinvention it is possible to manufacture a continuous flexible waveguideof relatively long length, the lengthusually being limited only by thesize of the take-up bobbin or storage means.

What is claimed is:

l. A method for continuously manufacturing a flexible waveguide havingan inner wall formed by a helically wound conductor and a tubular sheathof synthetic resin therearound, said method'comprising winding a helicalconductor into a helix with contacting turns around a support at a firstposition while simultaneously advancing said helix in the direction ofits axis, removing said helix from said support in a direction axiallythereof as the helix is formed and advancing and guiding said helix asit is formed to a second position located in said direction with respectto said support while maintaining the turns of the helix in the relationin which they were wound, said advancing, guiding and maintaining beingperformed by roller means located between said first and secondpositions, extruding a sheath of synthetic resin around said helix atsaid second position as it is advanced and synchronizing the rate ofwinding and advance of said helix as well as the rate of extrusion ofthe resin of said sheath so that the waveguide is formed continuouslywith the desired sheath therearound.

2. A method as set forth in claim 1 wherein said waveguide has a layerof plastic tape intermediate said helix and said sheath, said tapehaving a width greater than the distance between corresponding points onadjacent turns of said helix, said method further comprising wrappingsaid tape over the turns of said helix intermediate the point offormation of said helix and the extrusion of said sheath therearound,the wrapping of said tape being synchronized with the advance of saidhelix so that the waveguide is formed continuously.

3. Apparatus for continuously manufacturing a flexible waveguide havingan inner wall formed by a helically wound conductor and a tubular sheathof synthetic resin therearound, said apparatus comprising a support forsaid helix, a wire-distributor head for winding said conductor in ahelix with contacting turns around said support, means for feeding saidhelix from said support in a direction axially of said helix, means insaid direction with respect to said head for receiving said helix fromsaid support, for maintaining the turns of said helix in the desiredrelative positions and for advancing said helix in the direction of theaxis thereof at a speed synchronized with the rate at'which said helixis formed, and an extrusion head in said direction with respect to saidadvancing means for receiving said helix and extruding said sheaththereover as said helix is continuously formed and advanced.

4. Apparatus as set forth in claim 3 further comprising a tape lappinghead for wrapping tape on said helix disposed intermediate saidadvancing means and said extrusion head.

1. A method for continuously manufacturing a flexible waveguide havingan inner wall formed by a helically wound conductor and a tubular sheathof synthetic resin therearound, said method comprising winding a helicalconductor into a helix with contacting turns around a support at a firstposition while simultaneously advancing said helix in the direction ofits axis, removing said helix from said support in a direction axiallythereof as the helix is formed and advancing and guiding said helix asit is formed to a second position located in said direction with respectto said support while maintaining the turns of the helix in the relationin which they were wound, said advancing, guiding and maintaining beingperformed by roller means located between said first and secondpositions, extruding a sheath of synthetic resin around said helix atsaid second position as it is advanced and synchronizing the rate ofwinding and advance of said helix as well as the rate of extrusion ofthe resin of said sheath so that the waveguide is formed continuouslywith the desired sheath therearound.
 2. A method as set forth in claim 1wherein said waveguide has a layer of plastic tape intermediate saidhelix and said sheath, said tape having a width greater than thedistance between corresponding points on adjacent turns of said helix,said method further comprising wrapping said tape over the turns of saidhelix intermediate the point of formation of said helix and theextrusion of said sheath therearound, the wrapping of said tape beingsynchronized with the advance of said helix so that the waveguide isformed continuously.
 3. Apparatus for continuously manufacturing aflexible waveguide having an inner wall formed by a helically woundconductor and a tubular sheath of synthetic resin therearound, saidapparatus comprising a support for said helix, a wire-distributor headfor winding said conductor in a helix with contacting turns around saidsupport, means for feeding said helix from said support in a directionaxially of said helix, means in said direction with respect to said headfor receiving said helix from said support, for maintaining the turns ofsaid helix in the desired relative positions and for advancing saidhelix in the direction of the axis thereof at a speed synchronized withthe rate at which said helix is formed, and an extrusion head in saiddirection with respect to said advancing means for receiving said helixand extruding said sheath thereover as said helix is continuously formedand advanced.
 4. Apparatus as set forth in claim 3 further comprising atape lapping head for wrapping tape on said helix disposed intermediatesaid advancing means and said extrusion head.